Display and labeled article

ABSTRACT

A display includes a first optical effect layer including a first interface part, the first interface part being provided with recesses or protrusions arranged two-dimensionally at the minimum center-to-center distance of 200 nm to 500 nm, each of the recesses or protrusions having a forward-tapered shape, a reflective material layer covering at least a part of the first interface part, and a second optical effect layer including, at a position of a first portion of the first interface part that is covered with the reflective material layer, a portion that faces the reflective material layer with the first optical effect layer interposed therebetween or faces the first optical effect layer with the reflective material layer interposed therebetween, the second optical effect layer containing at least one of a cholesteric liquid crystal, a pearl pigment and a multilayer interference film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of PCT Application No.PCT/JP2010/068626, filed Oct. 21, 2010 and based upon and claiming thebenefit of priority from prior Japanese Patent Application No.2009-270445, filed Nov. 27, 2009, the entire contents of all of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical technique that offers, forexample, forgery prevention effect, decorative effect and/or aestheticeffect.

2. Description of the Related Art

Articles such as securities, certificates, brand goods, media forpersonal authentication, etc. are required to be difficult to forge.Thus, in some cases, a display excellent in forgery preventionperformance is provided on such articles.

Most of the displays include a microstructure such as diffractiongrating, hologram, lens array, etc. The microstructures are hard toanalyze. Further, in order to manufacture a display including themicrostructure, an expensive manufacturing apparatus such as electronbeam writer or the like is necessary. For these reasons, the displayslike this can achieve an excellent performance in forgery prevention.

For example, the patent literature 1 describes a display that includesfirst and second interface parts. The first interface part is providedwith grooves as a relief-type diffraction grating. The second interfacepart is provided with recesses or protrusions which are disposedtwo-dimensionally with a center-to-center distance smaller than theminimum center-to-center distance of the grooves and each of which has aforward tapered shape. The display has a fine structure and specialoptical characteristics. Accordingly, the display has an excellentperformance in forgery prevention.

PRIOR ART DOCUMENT Patent Literature

Patent Literature 1: Jpn. Pat. Appln. KOKAI Publication No. 2008-107470

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to realize a higher forgeryprevention effect.

According to a first aspect of the present invention, there is provideda display comprising a first optical effect layer including a firstinterface part, the first interface part being provided with recesses orprotrusions arranged two-dimensionally at the minimum center-to-centerdistance in a range of 200 nm to 500 nm, each of the recesses orprotrusions having a forward-tapered shape, a reflective material layercovering at least a part of the first interface part, and a secondoptical effect layer including, at a position of a first portion of thefirst interface part that is covered with the reflective material layer,a portion that faces the reflective material layer with the firstoptical effect layer interposed therebetween or faces the first opticaleffect layer with the reflective material layer interposed therebetween,the second optical effect layer containing at least one of a cholestericliquid crystal, a pearl pigment and a multilayer interference film.

According to a second aspect of the present invention, there is provideda labeled article comprising a substrate, and the display according tothe first aspect supported by the substrate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is plan view schematically showing a display according to anembodiment of the present invention;

FIG. 2 is a sectional view taken along a II-II line of the display shownin FIG. 1;

FIG. 3 is an enlarged perspective view showing an example of a structureadoptable in the second interface part of the display shown in FIGS. 1and 2;

FIG. 4 is an enlarged perspective view showing an example of a structureadoptable in the first interface part of the display shown in FIGS. 1and 2;

FIG. 5 is a diagram schematically showing an optical effect offered by aportion of the display shown in FIGS. 1 and 2 that corresponds to thesecond interface part;

FIG. 6 is a diagram schematically showing an optical effect offered by aportion of the display shown in FIGS. 1 and 2 that corresponds to thefirst interface part;

FIG. 7 is plan views schematically showing an example of arrangementpatterns of recesses or protrusions adoptable in the first interfacepart;

FIG. 8 is plan views schematically showing an example of arrangementpatterns of recesses or protrusions adoptable in the first interfacepart;

FIG. 9 is plan views schematically showing an example of arrangementpatterns of recesses or protrusions adoptable in the first interfacepart;

FIG. 10 is plan views schematically showing an example of arrangementpatterns of recesses or protrusions adoptable in the first interfacepart;

FIG. 11 is an enlarged perspective view showing another example of thestructure adoptable in the first interface part IF1 of the display shownin FIGS. 1 and 2;

FIG. 12 is an enlarged perspective view showing another example of thestructure adoptable in the first interface part IF1 of the display shownin FIGS. 1 and 2;

FIG. 13 is an enlarged perspective view showing another example of thestructure adoptable in the first interface part IF1 of the display shownin FIGS. 1 and 2;

FIG. 14 is a sectional view schematically showing a display according toa modification;

FIG. 15 is a sectional view schematically showing a display according toanother modification;

FIG. 16 is a sectional view schematically showing an adhesive labelaccording to an embodiment of the present invention;

FIG. 17 is a sectional view schematically showing a transfer foilaccording to an embodiment of the invention;

FIG. 18 is a plan view schematically showing an example of a labeledarticle;

FIG. 19 is a sectional view taken along a XIX-XIX line of the labeledarticle shown in FIG. 18;

FIG. 20 is a plan view schematically showing another example of alabeled article; and

FIG. 21 is a sectional view taken along a XXI-XXI line of the labeledarticle shown in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below withreference to drawings. In the drawings, the same reference symbolsdenote components having the same or similar functions and duplicatedescriptions will be omitted.

FIG. 1 is plan view schematically showing a display according to anembodiment of the present invention. FIG. 2 is a sectional view takenalong a II-II line of the display shown in FIG. 1. In FIGS. 1 and 2,directions in parallel with a main surface of the display 10 andorthogonal to each other are assigned as a X direction and a Ydirection, and a direction perpendicular to the main surface of thedisplay 10 is assigned as a Z direction.

The display 10 includes, as shown in FIG. 2, a substrate 11, a firstoptical effect layer 12, a reflective material layer 13, alight-transmitting layer 15, and a second optical effect layer 17. Aninterface between the first optical effect layer 12 and the reflectivematerial layer 13 includes a first interface part IF1, a secondinterface part IF2, and a third interfacial part IF3. As will bedescribed later, the first interface part IF1 is provided with aplurality of recesses or protrusions, and the second interface part IF2is provided with a plurality of grooves.

Hereinafter, a portion of the first interface part IF1 that is coveredwith the reflective material layer 13 is referred to as a first region.Further, a portion of the second interface part IF2 that is covered withthe reflective material layer 13 is referred to as a second region.Still further, a portion of the third interface part IF3 that is coveredwith the reflective material layer 13 is referred to as a third region.

In addition, hereinafter, a portion of the display 10 that correspondsto the first region is referred to as a display part DP1. Further, aportion of the display 10 that corresponds to the second region isreferred to as a display part DP2. Still further, a portion of thedisplay 10 that corresponds to the third region is referred to as adisplay part DP3.

A substrate 11 is, typically, a sheet or film of a resin. Examples ofthe resin include polyethylene terephthalate, polyethylene naphthalate,polycarbonate, triacetylcellulose, polypropylene, polymethylmethacrylate, acryl-styrene copolymer and vinyl chloride. The substrate11 may be omitted.

The first optical effect layer 12 is formed on the substrate 11. Thefirst optical effect layer 12 has, typically, light-transmittingproperties. Examples of materials of the first optical effect layer 12include resins such as thermoplastic resins, thermosetting resins, andUV- or electron beam-curable resins (hereinafter, also referred to asphoto-curable resin). When a thermoplastic resin, a thermosetting resinor a photo-curable resin is used as a material of the first opticaleffect layer 12, by transfer with an original plate, a recess structureand/or a protrusion structure can be readily formed on one main surface.

Examples of the thermoplastic resins with light-transmitting propertiesinclude polyethylene terephthalate, polyethylene naphthalate,polycarbonate, cellulose acetate, cellulose acetate lactate, celluloseacetate propionate, nitrocellulose, polyethylene, polypropylene,acryl-styrene copolymer, vinyl chloride and polymethyl methacrylate.

Examples of the thermosetting resins with light-transmitting propertiesinclude polyimide, polyamide, polyester urethane, acrylic urethane,epoxy urethane, silicone, epoxy and melamine resins.

The photo-curable resin is a resin that is cured by irradiating withlight such as UV-rays or electron beams. As a typical resin that causesa radical polymerization by light irradiation, an acrylic resin havingan acryloyl group in a molecule can be cited. For example, an epoxyacrylate-based, urethane acrylate-based, polyester acrylate-based orpolyol acrylate-based oligomer or polymer, a monofunctional,bifunctional or polyfunctional polymerizable (meth)acryl-based monomer(for example, tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate,2-hydroxy-3-phenoxypropyl acrylate, polyethylene glycol diacrylate,polypropylene glycol diacrylate, trimethylolpropane triacrylate,pentaerythritol triacrylate or pentaerythritol tetraacrylate) or anoligomer or a polymer thereof, or a mixture thereof can be used.

When a photo-curable resin is used as the material of the first opticaleffect layer 12, in this layer, a photopolymerization initiator may befurther contained. Examples of the photopolymerization initiatorsinclude benzophenone, diethyl thioxanthone, benzyl dimethyl ketal,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propane-1 andacylphosphine oxide. However, the photopolymerization initiator does notreact at 100% efficiency and an unreacted photopolymerization initiatormay adversely affect on the performance. Accordingly, it is preferablethat an amount of the photopolymerization initiator with respect to aphoto-curable resin is in the range of, for example, 0.1 to 7% by mass,typically, 0.5 to 5% by mass so that uncured portions do not remain.

On one main surface of the first optical effect layer 12, the interfaceparts IF1 to IF3 are disposed. The structures and opticalcharacteristics of the interface parts IF1 to IF3 will be described indetail later. One or both of the second interface part IF2 and the thirdinterface part IF3 may be omitted.

The reflective material layer 13 covers at least a part of the interfacepart IF1. FIGS. 1 and 2 show, as an example, a case where the reflectivematerial layer 13 covers entirely the interface parts IF1 to IF3.

As the reflective material layer 13, for example, a metal or alloy layermade of a metal material such as aluminum, silver, tin, chromium,nickel, copper, gold or alloys thereof can be used. In this case, thereflective material layer 13 is typically formed by use of a vacuumfilm-forming method. As the vacuum film-forming method, for example, avacuum evaporation method and a sputtering method can be cited. Athickness of the reflective material layer 13 is set, for example, inthe range of 1 nm to 100 nm.

The reflective material layer 13 plays a role of allowing the display 10to display an image excellent in visibility. Further, by providing thereflective material layer 13, it becomes difficult to damage the recessstructure and/or protrusion structure disposed on the main surface ofthe first optical effect layer 12.

The light-transmitting layer 15 is interposed between the reflectivematerial layer 13 and the second optical effect layer 17. Thelight-transmitting layer plays a role of enhancing the adhesivenessbetween the layers.

The light-transmitting layer 15 has light-transmitting properties, and,typically, is transparent. Examples of the materials of thelight-transmitting layer 15 include vinyl acetate resin, ethylene-vinylacetate copolymer resin, polyester resin, polyester urethane resin,acryl urethane resin, epoxy resin, epoxy urethane resin, polycarbonateurethane resin, butyral resin, and propylene chloride resin. Thelight-transmitting layer 15 may be omitted.

The second optical effect layer 17 includes a portion that faces thefirst optical effect layer 12 with the reflective material layer 13interposed therebetween at a position of a first portion of theinterface part IF1 that is covered with the reflective material layer13. FIGS. 1 and 2 show, as an example, a case where the second opticaleffect layer 17 faces an entirety of the first optical effect layer 12with the reflective material layer 13 interposed therebetween.

The second optical effect layer 17 includes at least one of acholesteric liquid crystal, a pearl pigment, and a multilayerinterference film.

When the second optical effect layer 17 includes a cholesteric liquidcrystal, the second optical effect layer 17 can be manufactured with,for example, a material containing a compound having a cholestericstructure, or, a material containing a compound to which a cholestericstructure is imparted by adding a chiral agent to a nematic liquidcrystal. In the cholesteric liquid crystal, for example, by changing anamount and a kind of the chiral agent added to the nematic liquidcrystal, the helical pitch thereof and a twist direction of apolarization plane can be changed. Further, at both ends of liquidcrystal molecule, a polymerizable group such as an acryl group or thelike can be introduced. When thus implemented, after each of liquidcrystal molecules is aligned, the alignment thereof can be readilyfixed.

When the second optical effect layer 17 includes the cholesteric liquidcrystal, the second optical effect layer 17 may be a layer of acholesteric liquid crystal or a layer containing a cholesteric liquidcrystal pigment.

When the second optical effect layer 17 is a layer of the cholestericliquid crystal, the light scattering in the second optical effect layer17 can be suppressed to the minimum.

When the second optical effect layer 17 is a layer containing thecholesteric liquid crystal pigment, the second optical effect layer 17contains typically powder of the cholesteric liquid crystal and atransparent binder. In this case, for example, by using a plurality ofthe cholesteric liquid crystal pigments mutually different in thehelical pitch and twist direction, the optical characteristics of thesecond optical effect layer 17 can be fine-tuned.

When the second optical effect layer 17 contains the cholesteric liquidcrystal, upon illuminating the second optical effect layer 17, thesecond optical effect layer 17 can emit selective reflected light havingcircularly-polarized properties. Hereinafter, it is assumed that an axisof orientation of the cholesteric liquid crystal is in nearly parallelwith a main surface of the display 10.

When a helical pitch of the cholesteric liquid crystal is P, an incidentangle with respect to an axis in parallel with a main surface of thedisplay 10 is θ, and a wavelength of reflected light is λ, it is knownthat the following equation is satisfied.2P·sin θ=nλ (n=1,2,3, . . . )

According to the equation, for example, when white light is incidentvertically to the second optical effect layer 17, that is, in the caseof θ=90°, a regularly reflected light having a wavelength of twice thehelical pitch P is emitted vertically to the second optical effect layer17.

For example, when a cholesteric liquid crystal having the helical pitchP of 280 nm is used, the second optical effect layer 17 can emit a light(wavelength λ=560 nm) corresponding to a green hue. Alternatively, whena cholesteric liquid crystal having the helical pitch P of 360 nm isused, the second optical effect layer 17 can emit a light(wavelength=720 nm) corresponding to a red hue. Like this, by varyingthe helical pitch P of the cholesteric liquid crystal, the opticalcharacteristics of the second optical effect layer 17 containing thecholesteric liquid crystal can be varied.

When the incident angle θ of the illumination light is made graduallysmaller, a wavelength of a light emitted from the second optical effectlayer 17 becomes gradually shorter, and, finally, shorter than theshortest wavelength of visible range. That is, by practicing like this,a hue of the emitted light varies from red to green, from green to blue,and finally, the emitted light becomes unrecognizable. For example, inthe case where a cholesteric liquid crystal having the helical pitch Pof 360° is used, when an incident angle θ is set at 30° (60° withrespect to a normal line direction of a main surface of the display 10),a wavelength of selectively reflected light is 360 nm. Accordingly, inthis case, an observer can not recognize visual effects due to thesecond optical effect layer 17 or is very difficult to recognize.

The second optical effect layer 17 containing a cholesteric liquidcrystal can be formed, for example, as follows.

According to the first method, firstly, a stretched film made of, forexample, polyethylene terephthalate, polypropylene, nylon, cellophane,polyvinyl alcohol or the like is prepared. The stretched film may berubbed. Then, a coating liquid is prepared by dissolving a raw materialof a cholesteric liquid crystal in an organic solvent. Subsequently, thestretched film is coated with the coating liquid. Thereafter, theresulted coated film is dried. Thereby, on the stretched film, liquidcrystal molecules are aligned. Then, in this state, it is illuminatedwith UV-ray to fix the alignment of the liquid crystal molecules. Thus,a cholesteric liquid crystal-forming film is obtained.

Next, a transfer-receiver, for example, one main surface of the firstoptical effect layer 12 or the reflective material layer 13 is coatedwith an adhesive having light-transmitting properties. Subsequently, thecholesteric liquid crystal-forming film is adhered thereto. Then, onlythe stretched film is peeled therefrom. Thus, on a transfer-receiver,for example, one main surface of the first optical effect layer 12 orthe reflective material layer 13, a second optical effect layer 17containing a cholesteric liquid crystal is formed.

According to the second method, firstly, a main surface on which thesecond optical effect layer 17 is formed, for example, one main surfaceof the first optical effect layer 12 or the reflective material layer 13is coated with an optical alignment ink. Thereafter, the coated film isdried and illuminated with polarizing UV-ray to form an alignment film.Then, a raw material of cholesteric liquid crystal is dissolved in anorganic solvent to prepare a coating liquid, and the alignment film iscoated with the coating liquid. Thereafter, the resulted coated film isdried to align liquid crystal molecules. Then, in this state, it isilluminated with UV-ray to fix the alignment of the liquid crystalmolecules. Thus, the second optical effect layer 17 containing thecholesteric liquid crystal is obtained. In this case, when theadhesiveness between a main surface on which the second optical effectlayer 17 is formed and the alignment film of an optical alignment ink isinsufficient, an anchoring layer may be further disposed.

In the above, a method where the liquid crystal molecules are alignedwith an alignment film was described, a method of aligning liquidcrystal molecules is not restricted to the method. For example, liquidcrystal molecules may be aligned by application of an electric fieldand/or a magnetic field or by application of shear stress.

Further, in the above, a method of fixing the alignment of the liquidcrystal molecules by UV-ray illumination was described. However, amethod of fixing the alignment of the liquid crystal molecules is notrestricted thereto. For example, the alignment of the liquid crystalmolecules may be fixed by quenching a layer containing the liquidcrystal molecules. Among these methods, a method of fixing the alignmentof the liquid crystal molecules by UV-ray illumination is morepreferred.

Form the viewpoint of the production cost of the display 10, among thefirst and second methods mentioned above, typically, the first method isadopted.

When the second optical effect layer 17 contains a pearl pigment, thesecond optical effect layer 17 may contain, for example, a layeredsubstance in a form of powder such as mica or the like, or powderobtained by coating the layered substance with a covering material suchas reduced titanium dioxide, iron oxide or the like. Alternatively, inthis case, the second optical effect layer 17 may contain powderobtained by pulverizing a multilayer interference film described below.When the second optical effect layer 17 contains the pearl pigment, thesecond optical effect layer 17 further contains typically a transparentbinder.

When the second optical effect layer 17 contains the pearl pigment, thesecond optical effect layer 17 is formed typically by a printing methodor a coating method. As the printing method or coating method, wellknown methods can be adopted.

A multilayer interference film that the second optical effect layer 17can contain is formed by stacking a plurality of layers havingrefractive indices different from each other. Each of the layersconstituting the multilayer interference film is, for example, a metalthin film, a ceramic thin film, or an organic polymer thin film. Themultilayer interference film contains, for example, an alternatelaminate of layers having refractive indices different from each other.For example, when a ceramic thin film or a metal thin film having thelight transmittance in the range of 20 to 70%, and an organic polymerthin film are alternately stacked at a predetermined thickness, amultilayer interference film that absorbs or reflects only a visiblelight having a specific wavelength can be obtained.

Examples of materials that can be adopted for the respective layers thatform the multilayer interference film will be described below. Anumerical value within parentheses following a chemical formula or aname of chemical compound is the refractive index of the compound.

Ceramics: Sb₂O₃ (3.0), Fe₂O₃ (2.7), TiO₂ (2.6), CdS (2.6), CeO₂ (2.3),ZnS (2.3), PbCl₂ (2.3), CdO (2.2), Sb₂O₃ (2.0), WO₃ (2.0), SiO (2.0),Si₂O₃ (2.5), In₂O₃ (2.0), PbO (2.6), Ta₂O₃ (2.4), ZnO (2.1), ZrO₂ (2.0),MgO (1.6), Si₂O₂ (1.5), MgF₂ (1.4), CeF₃ (1.6), CaF₂ (1.3 to 1.4), AlF₃(1.6), Al₂O₃ (1.6) and GaO (1.7).

Metal: Al, Fe, Mg, Zn, Au, Ag, Cr, Ni, Cu, Si, and alloys thereof.

Organic polymer: polyethylene (1.51), polypropylene (1.49),polytetrafluoroethylene (1.35), polymethyl methacrylate (1.49), andpolystyrene (1.60).

When the second optical effect layer 17 contains the multilayerinterference film, the second optical effect layer 17 can be formed byuse of a known method that can control a film thickness, a film-formingspeed, the number of laminated layers and an optical film thickness.Examples of such methods include a vacuum evaporation method, asputtering method and a chemical vapor deposition method (CVD method).The optical film thickness means a product of the refractive index and afilm thickness.

Alternatively, the multilayer interference film may be a multilayer filmformed by coextrusion of multiple layers. The multilayer film thusobtained is an alternate laminate of a plurality of plastic thin filmshaving the refractive indices different from each other. Each of theplastic thin films contains a plastic material. Each of the plastic thinfilms may further contain an additive as required.

The multilayer film contains, for example, an alternate laminate ofplastic thin films having the refractive indices different from eachother. Examples of the materials of the plastic thin films includepolyethylene naphthalate (1.63), polycarbonate (1.59), polystyrene(1.59), polyethylene terephthalate (1.58), nylon (1.53), polymethylmethacrylate (1.49), polymethyl pentene (1.46) and fluorinatedpolymethyl methacrylate (1.4). It is particularly preferable to use analternate laminate of a thin film of polyethylene naphthalate (1.63) anda thin film of polyethylene terephthalate (1.58) as the multilayer film.

In the case where the second optical effect layer 17 contains themultilayer interference film, compared with the case where the secondoptical effect layer 17 contains the cholesteric liquid crystal or thepearl pigment, the crack resistance of the display 10 is higher.Further, in the case where the second optical effect layer 17 containsthe multilayer interference film, compared with the case where thesecond optical effect layer 17 contains the cholesteric liquid crystal,the light resistance of the display 10 is higher. In addition, in thecase where the second optical effect layer 17 contains the multilayerinterference film, compared with the case where the second opticaleffect layer 17 contains the cholesteric liquid crystal or the pearlpigment, the production cost of the display 10 is lower.

The second optical effect layer 17 varies in color depending on anobservation angle. The optical characteristics due to a combination ofthe second optical effect layer 17, the first optical effect layer 12,and the reflective material layer 13 will be display part later.

FIG. 3 is an enlarged perspective view showing an example of a structureadoptable in the second interface part of the display shown in FIGS. 1and 2. FIG. 4 is an enlarged perspective view showing an example of astructure adoptable in the first interface part of the display shown inFIGS. 1 and 2.

The second interface part IF2 is provided with a relief-type diffractiongrating configured by disposing a plurality of grooves 14 a. The minimumcenter-to-center distance of the grooves 14 a is larger than the minimumcenter-to-center distance of the plurality of recesses or protrusions 14b described later. The minimum center-to-center distance of the grooves14 a is, for example, the shortest wavelength of visible range or more,typically, in the range of 0.5 μm to 2 μm. Further, a depth of thegroove 14 a is, for example, in the range of 0.05 μm to 1 μm, typically,in the range of 0.05 μm to 0.3 μm. The second interface part IF2 may beomitted.

The term “diffraction grating” means a structure that generates adiffracted light by illuminating with an illumination light such asnatural light, and encompasses, in addition to an ordinary diffractiongrating where a plurality of grooves 14 a is arranged in parallel and atan equidistance, an interference pattern recorded in a hologram.Further, a groove 14 a or a portion sandwiched between grooves 14 a willbe called as a “grating line”.

The first interface part IF1 is provided with a plurality of recesses orprotrusions 14 b. These recesses or protrusions 14 b are twodimensionally arranged with the minimum center-to-center distance in therange of 200 nm to 500 nm. The recesses or protrusions 14 b are disposedtypically regularly. Each of the recesses or protrusions 14 b has aforward tapered shape. A depth or height of each of the recesses orprotrusions 14 b is usually larger than the depth of the groove 14 a,typically in the range of 0.3 μm to 0.5 μm. A ratio of the depth orheight to the minimum center-to-center distance of the recesses orprotrusions 14 b (hereinafter, referred to also as aspect ratio) is, forexample, in the range of 0.5 to 1.5.

The third interface part IF3 is a flat surface. The third interface partIF3 may be omitted.

It is difficult to accurately analyze, from a completed display 10, afine structure on the first interface part IF1. Further, even if theabove-mentioned fine structure could be analyzed from the completeddisplay 10, it is difficult to forge or imitate the display containingthe fine structure. In the case of the diffraction grating, according toan optical duplication method that makes use of laser light, thestructure may be copied as an interference pattern. However, the finestructure on the first interface part IF1 is impossible to copy.

Optical effects due to a combination of the first optical effect layer12, the reflective material layer 13 and the second optical effect layer17 will be described below.

Firstly, an optical effect of a display part DP2 will be described.

FIG. 5 is a diagram schematically showing an optical effect offered by aportion of the display shown in FIGS. 1 and 2 that corresponds to thesecond interface part. In FIG. 5, 31 a indicates an illumination light,32 a indicates a regularly reflected light or 0th-order diffractedlight, and 33 a indicates the 1st-order diffracted light. In FIG. 5, thefirst optical effect layer 12 and the reflective material layer 13 arenot shown.

When a diffraction grating is illuminated, the diffraction grating emitsa diffracted light 33 a strong in a specific direction relative to atraveling direction of the illumination light 31 a, which is an incidentlight. When a light travels in a plane perpendicular to the gratinglines of the diffraction grating, an angle of emergence of them-th-order diffracted light can be calculated from the followingequation (1) (m=0, ±1, ±2, . . . ).d=mλ/(sin α−sin β)  (1)

In the equation (1), d represents a grating constant of the diffractiongrating, and λ, represents a wavelength of incident light and diffractedlight. Further, α represents an angle of emergence of a 0th-orderdiffracted light, that is, a transmission light or regularly reflectedlight. In other words, an absolute value of α is equal with an incidentangle of the illumination light and in a relationship symmetrical withthe incident angle relative to a z axis (in the case of reflection-typediffraction grating). As to α and β, a clockwise direction from the zaxis is taken as a positive direction.

The most typical diffracted light is the 1st-order diffracted light 33a. As obvious from the equation (1), an angle of emergence β of the1st-order diffracted light varies in accordance with a wavelength λ.That is, the diffraction grating has a function as a spectrometer.Accordingly, in the case where the illumination light is white light,when an observation angle is changed in a plane perpendicular to agrating line of the diffraction grating, a color recognized by anobserver is also changed.

Further, a color recognized by an observer under a certain observationcondition varies in accordance with the grating constant d.

As an example, it is assumed that the diffraction grating emits the1st-order diffracted light 33 a in a direction normal to the diffractiongrating. That is, it is assumed that an angle of emergence β of the1st-order diffracted light 33 a is 0°. Further, it is assumed that anobserver perceives the 1st-order diffracted light 33 a. At this time,when an angle of emergence of the 0th-order diffracted light 32 a isα_(N), the equation (1) can be simplified to the following equation (2).d=λ/sin α_(N)  (2)

As obvious from the equation (2), in order to make an observer torecognize a specific color, a wavelength λ corresponding to the color,an incident angle |α_(N)| of the illumination light 31 a and the gratingconstant d may well be set so as to satisfy the relationship shown bythe equation (2). For example, white light containing all lightcomponents in the range of wavelength of 400 nm to 700 nm is used as anillumination light 31 a, and an incident angle |α_(N)| of theillumination light 31 a is set to 45°. Then, a diffraction grating ofwhich spatial frequency (inverse number of grating constant) distributesin the range of 1,000 lines/mm to 1,800 lines/mm is used. In this case,when the diffraction grating is observed from the normal direction, aportion where the spatial frequency is about 1,600 lines/mm is seenblue-colored, and a portion where the spatial frequency is about 1,100lines/mm is seen red-colored.

The diffraction grating having a smaller spatial frequency is easy toform. Accordingly, in an ordinary display, majority of the diffractiongratings are diffraction gratings having a spatial frequency from 500lines/mm to 1,600 lines/mm.

Thus, a color recognized by an observer under a certain observationcondition can be controlled by the grating constant d (or spatialfrequency) of the diffraction grating. And, when the observation angleis varied from the previous observation condition, a color recognized bythe observer varies.

In the above description, it is assumed that light travels in a planeperpendicular to the grating lines. When, an orientation of the gratingline is changed from this state to rotate with a normal line of a mainsurface of the display 10 as an axis of rotation, an effective value ofthe grating constant d for a constant observation direction varies inaccordance with an angle of the grating line (hereinafter, also referredto as azimuth angle) relative to a reference state. As the resultthereof, a color recognized by an observer varies. Conversely, when aplurality of diffraction gratings different only in the orientation ofthe grating lines is disposed, these diffraction gratings can displaydifferent colors. Further, when the azimuth angle becomes large enough,diffracted light can not be recognized from the constant observationdirection the same as the case where there is no diffraction grating. Bymaking use of this, by use of two or more kinds of diffraction gratingslargely different in the orientation of the grating line, when observedfrom directions corresponding to the respective grating lines, imagesindependent from each other can be displayed as well.

Further, when a depth of the grooves 14 a that constitute thediffraction grating is made deeper, depending on a wavelength of theillumination light 31 a and so on, the diffraction efficiency varies.When an area ratio of the diffraction grating to a pixel is made larger,the intensity of the diffracted light becomes stronger.

Accordingly, in the case where the second interface part IF2 is formedby arranging a plurality of pixels, when spatial frequencies and/orazimuth angles of the grooves 14 a are made different between one ormore pixels and other pixel(s), the former and the latter can displaydifferent colors, and, further, an observable condition can be set.Further, when at least one of the depth of the groove 14 a and/or thearea ratio of the diffraction grating to the pixel is made differentbetween one or more of the pixels and other pixel(s) that constitute thesecond interface part IF2, the brightness of the pixels can bedifferentiated. Accordingly, by making use thereof, the second interfacepart IF2 can display an image such as a full-color image, a stereo-imageor the like.

The term “image” here means what can be observed as a spatialdistribution of color and/or brightness. The “image” encompassesphotographs, figures, paintings, characters, marks and so on.

A portion of the second optical effect layer 17 that corresponds to thesecond interface part IF2 emits light different in wavelength dependingon an observation angle. However, the intensity of the diffracted lightemitted by a portion of the second interface part IF2 that is coveredwith the reflective material layer 13 is far higher than the intensityof light emitted by the corresponding portion of the second opticaleffect layer 17. Accordingly, the display part DP2 is usually observedas a region where a diffraction grating is disposed.

Next, an optical effect of the display part DP1 will be described.

FIG. 6 is a diagram schematically showing an optical effect offered by aportion of the display shown in FIGS. 1 and 2 that corresponds to thefirst interface part. In FIG. 6, 31 b and 31 c each indicates anillumination light, 32 b and 32 c each indicates a regularly reflectedlight or a 0th-order diffracted light, and 33 b indicates a 1st-orderdiffracted light. In FIG. 6, the first optical effect layer 12 and thereflective material layer 13 are not shown.

When the interface part IF1 and the interface part IF2 are provided, therecesses or protrusions 14 b on the first interface part IF1 arearranged at the center-to-center distance smaller than the minimumcenter-to-center distance of the grooves 14 a. Accordingly, even whenthe recesses and protrusions 14 b are regularly arranged and the firstinterface part IF1 emits the diffracted light 33 b, the observer doesnot simultaneously recognize the diffracted light 33 b and thediffracted light 33 a from the second interface part IF2 having the samewavelength therewith. In particular, when the difference between theminimum center-to-center distance of the grooves 14 a, that is, thegrating constant of the diffraction grating, and the center-to-centerdistance of the recesses or protrusions 14 b is large enough,irrespective of the wavelength, the observer can not simultaneouslyrecognize the diffracted light 33 a from the second interface part IF2and the diffracted light 33 b from the first interface part IF1.However, as obvious from the equation (1), when a high-order diffractedlight (|m|≧2) is generated, within an observation angle capable ofrecognizing a high-order diffracted light 33 a from the second interfacepart IF2, also the diffracted light 33 b from the first interface partIF1 can be made recognizable.

Further, each of the recesses or protrusions 14 b has a forward taperedshape. Accordingly, when observed from whatever angle, the reflectanceof the first interface part IF1 for the regularly reflected light issmall.

In addition, when an angle of emergence of the 1st-order diffractedlight 33 b from the first interface part IF1 is larger than −90°, byproperly adjusting an angle that the observation direction and a normalline direction of the display 10 form, the observer can recognize the1st-order diffracted light 33 b from the first interface part IF1.Therefore, in this case, it can be visually confirmed that the displayDP1 is different from a portion that is composed only of a layercontaining at least one of the cholesteric liquid crystal, pearl pigmentand multilayer interference film.

As described above, the minimum center-to-center distance of therecesses or protrusions 14 b is in the range of 200 nm to 500 nm. Whenthe minimum center-to-center distance is made smaller, in some cases, itis difficult to make the diffracted light from the interface part IF1emerge. When the minimum center-to-center distance is made larger, insome cases, the intensity of the diffracted light emitted at arelatively small angle of emergence from the first interface part IF1becomes relatively large.

The minimum center-to-center distance of the recesses or protrusions 14b may be, for example, in the range of 200 nm to 350 nm. In this case,as obvious from the equation (1), in the first interface part IF1, thediffracted light having a wavelength corresponding to blue light can bereadily observed. Accordingly, for example, when the second interfacepart IF2 emits the diffracted light having a wavelength corresponding tored color, by comparing both, the display 10 is more readily confirmedto be a authentic article.

Alternatively, the minimum center-to-center distance of the recesses orprotrusions 14 b may be in the range of 300 nm to 500 nm. Whenimplemented like this, a range of angle where the 1st-order diffractedlight 33 b emitted by the recesses or protrusions 14 b can be observedbecomes relatively wide. That is, when implemented like this, aauthentic article to which the recesses or protrusions 14 b are providedand a forged article to which the recesses or protrusions 14 b are notprovided can be readily differentiated.

As described above, the reflectance of the first interface part IF1 forthe regularly reflected light is small. Further, the intensity of thediffracted light emitted by the first interface part IF1 at a relativelysmall angle of emergence is zero or very small. Accordingly, theregularly reflected light or diffracted light emitted by the firstinterface part IF1 have a relatively small effect on light emitted by aportion of the second optical effect layer 17 that corresponds to thefirst interface part IF1. Therefore, at the display part DP1, an opticaleffect due to the second optical effect layer 17 can be very clearlyrecognized by the observer.

The first interface part IF1 may include a plurality of regions that aredifferent from each other in at least one of a shape, a depth or height,a center-to-center distance, and a pattern of arrangement of therecesses or protrusions 14 b. In this case, each of the portionscorresponding to the plurality of regions can exert an optical effectdifferent from each other.

Further, in the case where the first interface part IF1 is configured byarranging a plurality of pixels, when one or more of the pixels andother pixel(s) are differentiated in at least one of a shape, a depth orheight, a center-to-center distance, and a pattern of arrangement of therecesses or protrusions 14 b, their reflectances or the like can bedifferentiated. Accordingly, by making use of this, the first interfacepart IF1 can display a gray-scale image.

Still further, in the display 10, the second interface part IF2 and thefirst interface part IF1 are in the same plane. Accordingly, forexample, when a recess structure and/or a protrusion structurecorresponding the grooves 14 a and the recesses or protrusions 14 b isformed on an original plate, and the recess structure and/or theprotrusion structure is transferred onto the first optical effect layer12, the grooves 14 a and the recesses or protrusions 14 b can besimultaneously formed. Therefore, when the recess structure and/or theprotrusion structure is formed with high precision on an original plate,a problem of the position displacement between the second interface partIF2 and the first interface part IF1 is not generated. Further, featuresof a fine concavo-protrusion structure and high precision allows todisplay a high definition image and make easy to differentiate it froman article produced according to other method. Further, a fact thatauthentic articles can be stably manufactured with very high precisionmake easier to differentiate these from forged articles and imitationarticles.

Next, an optical effect of the display part DP3 will be described.

The third interface part IF3 is, as was described above, a flat surface.Accordingly, a portion of the third interface part IF3 that is coveredwith the reflective material layer 13 specularly reflects illuminationlight. The intensity of the reflected light is far stronger than that oflight emitted by the corresponding portion of the second optical effectlayer 17. As the result thereof, the display part DP3 is usuallyobserved as a mirror surface.

The display 10 shown in FIGS. 1 and 2 offers a very special visualeffect depending on an incident angle of illumination light and anobservation angle of an observer.

Hereinafter, with a direction normal to the display 10 as a referencedirection, an angular range that includes a direction of emergence of aregularly reflected light for a specific illumination light is referredto as a “positive angular range”, and an angular range including anincident direction of the specific illumination light is referred to asa “negative angular range”. The illumination light is assumed to bewhite light.

Firstly, a case where the illumination light is incident only at anangle within a negative angular range and the display 10 is observed atan angle within a positive angular range will be considered. In thiscase, as was described above, the display part DP1 very clearly exhibitsthe optical effect due to the second optical effect layer 17. That is,the display part DP1 is visually recognized as a region that showsdifferent colors in accordance with an observation angle. Further, inthis case, the display part DP2 is usually observed as a region wherethe diffraction grating is disposed. That is, at the display part DP2, adiffracted light whose wavelength varies in accordance with theobservation angle is recognized. Also, in this case, the display partDP3 is usually observed as a mirror surface. That is, at the displaypart DP3, when observed at an angle capable of observing regularlyreflected light, light having the same wavelength as that of theillumination light is recognized. As above, when observing the display10 at an angle within a positive angular range, the display 10 isobserved to include a region that exhibits different colors inaccordance with an observation angle, a region provided with adiffraction grating, and a region provided with a mirror surface.

Then, a case where the illumination light is incident only at an anglewithin the negative angular range and the display 10 is observed at anangle within the negative angular range will be considered. In thiscase, when an incident angle of the illumination light and anobservation angle are wide, that is, when absolute values of theincident angle and observation angle are large, the observer canrecognize diffracted light from the display part DP1. Accordingly, forexample, when a position of a light source of the illumination light anda position of the observer are fixed and an angle between these and thedisplay 10 is continued to change, a discontinuous variation of thevisual effect is generated in the display part DP1. Specifically, whenthe incident angle and the observation angle are made wider, thediffracted light from the display part DP1 can be observed at a certainangle.

Subsequently, assuming a room interior where fluorescent lamps aredisposed at a plurality of places, supposed is a case where two or morelight sources of illumination light are present. As an example, supposedis a case where a first light source that makes an illumination lightincident at an angle within a negative angular range and a second lightsource that makes an illumination light incident at an angle within apositive angular range are present. In this case, for example, whenpositions of the first and second light sources and the position of theobserver are fixed and an angle between these and the display 10 ischanged, a discontinuous change of the visual effect is generated in thedisplay part DP1. Specifically, when the observation angle is narrow, acontinuous change of color due to the second optical effect layer 17 isgenerated in the display part DP1. When the incident angle andobservation angle are made wider, the diffracted light from the displaypart DP1 becomes observable at certain angles or wider.

In the display 10 shown in FIGS. 1 and 2, the first interface part IF1and the second interface part IF2 are located adjacent to each other.The reflective material layer 13 covers both of the first interface partIF1 and the second interface part IF2 such that it crosses over theboundary therebetween. Further, the second optical effect layer 17 isdisposed so that an orthogonal projection of the second optical effectlayer 17 on a main surface of the first optical effect layer 12containing the interface parts IF1 and IF2 crosses over the boundarybetween the first interface part IF1 and the second interface part IF2.

The boundary between the first interface part IF1 and the secondinterface part IF2 can be defined with high precision according to anelectron beam lithography method and a nano-imprinting method.Accordingly, when such a configuration is adopted, the boundary betweenthe display part DP1 and the display part DP2 can be defined at highprecision. Accordingly, when implemented like this, the display 10 candisplay a high definition pattern corresponding to the boundary betweenthe first interface part IF1 and the second interface part IF2.

In the display 10 shown in FIGS. 1 and 2, the first interface part IF1and the third interface part IF3 are located adjacent to each other. Thereflective material layer 13 covers both of the first interface part IF1and the third interface part IF3 so as to cross over a boundarytherebetween. Further, the second optical effect layer 17 is disposed sothat its orthogonal projection on a main surface of the first opticaleffect layer 12 including the interface parts IF1 and IF3 crosses over aboundary between the first interface part IF1 and the second interfacepart IF3.

The boundary between the first interface part IF1 and the thirdinterface part IF3 can be defined with high precision according to anelectron beam lithography method and a nano-imprinting method.Accordingly, when such a configuration is adopted, the boundary betweenthe display part DP1 and the display part DP3 can be defined at highprecision. Accordingly, by implementing like this, the display 10 candisplay a high definition pattern corresponding to the boundary betweenthe first interface part IF1 and the third interface part IF3.

As above, the display 10 has a very specific visual effect. It isimpossible or very difficult for a person who tries to forge toreproduce the visual effect like this. That is, the display 10 has avery high forgery prevention effect.

When the second optical effect layer 17 contains the cholesteric liquidcrystal, the second optical effect layer 17 can emitcircularly-polarized light as selective reflected light. Further, thepresent inventors have found that the diffracted light emitted by thefirst interface part IF1 has linearly-polarized characteristics.Accordingly, when the second optical effect layer 17 contains thecholesteric liquid crystal, based on the difference in the polarizationproperties, change of the emitted light can be tracked. That is, in thiscase, the display 10 is useful also as a forgery prevention medium forcovert use.

As a method of discriminating an article whose genuineness is unknownbetween a authentic article and a non-authentic article, for example,the following methods can be mentioned.

Firstly, as a first operation, the display 10 is illuminated withillumination light at an incident angle whose absolute value is lessthan 60°. At this time, it is confirmed that the optical effect causedby the second optical effect layer 17 can be observed within an angularrange with an absolute value of less than 60°. For example, when thesecond optical effect layer 17 contains the cholesteric liquid crystal,it is confirmed that the second optical effect layer 17 emits theselective reflected light within the angular range.

Then, as a second operation, the display 10 is illuminated withillumination light at an incident angle whose absolute value is 60° ormore and less than 90°. At this time, it is confirmed that the opticaleffect caused by the first interface part IF1 is observed within anangular range whose absolute value is 60° or more and less than 90° andwhich has the same polarity as that of the angular range for theincident angle. That is, it is confirmed that the diffracted light fromthe first interface part IF1 can be observed within this angular range.

When the above-mentioned optical effects are observed in both of thefirst and second operations, the present article is judged as aauthentic article. On the other hand, when the above-mentionedrespective optical effects are not observed in one or both of the firstand second operations, the present article is judged as a non-authenticarticle.

When the second optical effect layer 17 contains the cholesteric liquidcrystal, the discrimination between a authentic article and anon-authentic article may be conducted as described below. That is,when, in the first operation, a circularly-polarized light is emitted inan angular range within which the absolute value of angle is less than60°, and, in the second operation, a linearly polarized light is emittedin an angular range within which the absolute value of angle is 60° ormore and less than 90° and which has the same polarity as that of theangular range including the incident angle, the article may be judged asa authentic article. The discrimination can be performed by observingthe display 10 through a polarization plate such as a circularlypolarizing plate or a linearly polarizing plate.

FIGS. 7 to 10 are plan views schematically showing examples ofarrangement patterns of recesses or protrusions adoptable in the firstinterface part.

In FIG. 7, the arrangement of the recesses or protrusions 14 b forms asquare lattice. The structure can be relatively easily manufactured byuse of a micro-fabrication machine such as an electron beam writer or astepper, and the center-to-center distance of the recesses orprotrusions 14 b can be relatively easily controlled at high precision.

In FIG. 7, the center-to-center distances of the recesses or protrusions14 b are set equal in X direction and Y direction. However, thecenter-to-center distances of the recesses or protrusions 14 b may beset differently in X direction and Y direction. That is, the arrangementof the recesses or protrusions 14 b may form a rectangular lattice.

When the center-to-center distances of the recesses or protrusions 14 bare set relatively long both in X direction and Y direction, the firstinterface part IF1 can emit diffracted light in either of the case wherethe display 10 is illuminated in a direction perpendicular to the Ydirection and the case where the display 10 is illuminated in adirection perpendicular to the X direction, and the wavelengths of thediffracted lights can be differentiated between the former case and thelatter case. When the center-to-center distance of the recesses orprotrusions 14 b is set relatively longer in one direction of the Xdirection and Y direction and the other is set relatively shorter, thefirst interface part IF1 emits diffracted light in the case where thedisplay 10 is illuminated in a direction perpendicular to one of the Xdirection and Y direction, and the diffracted light can be inhibitedfrom emerging from the first interface part IF1 in the case where thedisplay 10 is illuminated in a direction perpendicular to the otherdirection of the X direction and Y direction.

In FIG. 8, the arrangement of the recesses or protrusions 14 b forms atriangular lattice. In the case where the structure is adopted and thecenter-to-center distance of the recesses or protrusions 14 b isproperly set, the diffracted light can be inhibited from emerging fromthe first interface part IF1, for example, when the display 10 isilluminated in an A direction, and the first interface part IF1 can emitthe diffracted light when the display 10 is illuminated in a B directionand a C direction. That is, more complicated visual effects can beobtained.

In FIG. 9, the recesses or protrusions 14 b are randomly arranged. Whenthe recesses or protrusions 14 b are randomly arranged, emission of thediffracted light by the first interface part IF1 becomes less prone tooccur. The structure can be formed by recording an intensitydistribution of speckles by making use of, for example, interference oflight.

In FIG. 10, in addition to that the recesses or protrusions 14 b arerandomly arranged, their sizes are uneven. In the case where thestructure is adopted, as compared with the case where the structure ofFIG. 9 is adopted, emission of the diffracted light by the firstinterface part IF1 becomes further less prone to occur.

As illustrated in FIGS. 7 to 10, the arrangement pattern of the recessesor protrusions 14 b can be variously modified. Each of the respectivearrangement patterns offers an inherent visual effect. Accordingly, whenthe first interface part IF1 is formed of a plurality of pixelsdifferent in the arrangement pattern of the recesses or protrusions 14b, more complicated visual effects can be obtained.

FIGS. 11 to 13 are enlarged perspective views showing other examples ofthe structure adoptable in the first interface part IF1 of the displayshown in FIGS. 1 and 2.

Structures shown in FIGS. 11 to 13 are modification examples of thestructure shown in FIG. 4. Each of the recesses or protrusions 14 bshown in FIGS. 11 to 13 has a forward tapered shape.

In the structure shown in FIG. 4, each of the recesses or protrusions 14b has a conical shape. When each of the recesses or protrusions 14 b isformed in a shape of cone, each of the recesses or protrusions 14 b mayhave a pointed tip or a truncated conical shape. When employing aconical shape in the recesses or protrusions 14 b, the recesses orprotrusions 14 b may have a pointed tip or be truncated. In the casewhere each of the recesses or protrusions 14 b has a conical shape witha pointed tip, the reflectance of the first interface part IF1 for theregularly reflected light can be made smaller as compared with the casewhere each of the recesses or protrusions 14 b has a truncated conicalshape because in the former case, the recesses or protrusions 14 have nosurface that is parallel with the first interface portion.

In the structure shown in FIG. 11, each of the recesses or protrusions14 b has a square pyramidal shape. The recesses or protrusions 14 b mayhave a pyramidal shape other than the square pyramid such as atriangular pyramid or the like. In this case, the intensity of thediffracted light generated under a specific condition can be enhanced,thereby the observation is made easier. Further, when the recesses orprotrusions 14 b are formed in pyramid, each of the recesses orprotrusions 14 b may have a pointed tip or a truncated pyramidal shape.In the case where each of the recesses or protrusions 14 b has a pointedpyramidal shape, the reflectance of the first interface part IF1 for theregularly reflected light can be made smaller as compared with the casewhere each of them has a truncated shape because in the former case, therecesses or protrusions 14 b do not have a plane in parallel with thefirst interface part IF1.

In the structure shown in FIG. 12, each of the recesses or protrusions14 b has a half-spindle shape. That is, the recess or protrusion 14 bhas a conical shape with a rounded tip. In the case where the structureshown in FIG. 12 is adopted, formation of a protrusion structure and/ora recess structure on an original plate and transfer of the protrusionstructure and/or the recess structure from the original plate to thefirst optical effect layer 12 are easy as compared with the case wherethe structure shown in FIG. 4 or 11 is adopted.

In the structure shown in FIG. 13, each of the recesses or protrusions14 b has a structure in which a plurality of quadrangular prismsdifferent in bottom area is stacked in order from a quadrangular prismhaving larger bottom area. In place of the quadrangular prisms, prismsother than the quadrangular prisms such as circular prisms or triangularprisms may be stacked.

In the case where the structure shown in FIG. 13 is adopted, thereflectance of the first interface part IF1 for the specularly reflectedlight cannot be made small as compared with the case where the structureshown in FIG. 4, 11 or 12 is adopted. However, in the case where thestructure shown in FIG. 13 is adopted, similarly to the case where thestructure shown in FIG. 12 is adopted, formation of a protrusionstructure and/or a recess structure on an original plate and transfer ofthe protrusion structure and/or the recess structure from the originalplate to the first optical effect layer 12 are easy as compared with thecase where the structure shown in FIG. 4 or 11 is adopted.

As above, the shape of the recess or protrusion 14 b affects thereflectance of the first interface part IF1. Accordingly, when the firstinterface part IF1 is formed of a plurality of pixels different in theshapes of the recesses or protrusions 14 b, the first interface part IF1can display a gray-scale image.

The minimum center-to-center distance of the recesses or protrusions 14b is in the range of 200 nm to 500 nm as described above. When theminimum center-to-center distance is adjusted, the visual effect of thedisplay 10 can be adjusted. For example, when the minimumcenter-to-center distance of the recesses or protrusions 14 b is set at400 nm or less, as obvious from the equation (2), for all wavelengths inthe visible range, i.e., a range of 400 nm to 700 nm, irrespective ofthe incident angle of the illumination light, the first interface partIF1 is inhibited from emitting the diffracted light in the normaldirection. Accordingly, when implemented like this, the optical effectin the display part DP1 caused by the second optical effect layer 17 canbe more clearly recognized. Further, when the first interface part IF1is formed of a plurality of pixels different in the center-to-centerdistance of the recesses or protrusions 14 b, the first interface partIF1 can display a gray-scale image.

When the depth or height of the recesses or protrusions 14 b on thefirst interface part IF1 is made larger, for example, one half or largerof the minimum center-to-center distance thereof, the intensity of thereflected light emitted by the first interface part IF1 can be madesmaller. Accordingly, by implementing like this, the optical effect inthe display part DP1 caused by the second optical effect layer 17 can bemore clearly recognized. Further, when the first interface part IF1 isformed of a plurality of pixels different in the depth or height of therecesses or protrusions 14 b, the first interface part IF1 can display agray-scale image.

When a ratio of a dimension of the recess or protrusion 14 b in adirection parallel with the first interface part IF1 to thecenter-to-center distance of the recesses or protrusions 14 b in thisdirection is made closer to 1:1, the intensity of the reflected lightemitted by the first interface part IF1 becomes smaller. When adimension of the recess or protrusion 14 b in a direction parallel withthe first interface part IF1 are made equal to the center-to-centerdistance of the recesses or protrusions 14 b in this direction, theintensity of the reflected light emitted by the first interface part IF1becomes the smallest. Accordingly, when implemented like this, theoptical effect due to the second optical effect layer 17 in the displaypart DP1 can be more clearly recognized. Further, when the firstinterface part IF1 is formed of a plurality of pixels different in theabove ratio, the first interface part IF1 can display a gray-scaleimage.

Various modifications can be made on the display 10 shown in FIGS. 1 and2.

FIG. 14 is a sectional view schematically showing a display according toa modification. The display 10 shown in FIG. 14 has a structure similarto that of the display shown in FIGS. 1 and 2 except that the reflectivematerial layer 13 covers only a part of the first interface part IF1, apart of the second interface part IF2 and a part of the third interfacepart IF3.

Hereinafter, a portion of the first interface part IF1 that is notcovered with the reflective material layer 13 is referred to as a fourthregion. Further, a portion of the second interface part IF2 that is notcovered with the reflective material layer 13 is referred to as a fifthregion. And, a portion of the third interface part IF3 that is notcovered with the reflective material layer 13 is referred to as a sixthregion.

In addition, hereinafter, a portion of the display 10 that correspondsto the fourth region is referred to as a display part DP1′. Further, aportion of the display 10 that corresponds to the fifth region isreferred to as a display part DP2′. And, a portion of the display 10that corresponds to the sixth region is referred to as a display partDP3′.

In the display 10 shown in FIG. 14, the reflective material layer 13covers only a part of the first interface part IF1. And, the secondoptical effect layer 17 has a portion that faces the first opticaleffect layer 12 at a position of a portion of the first interface partIF1 that is not covered with the reflective material layer 13.

In the display part DP1′, the first interface part IF1 is not coveredwith the reflective material layer 13. Accordingly, the display partDP1′ offers a visual effect almost the same as that offered in the casewhere the first interface part IF1 does not exist. That is, theintensity of the diffracted light emitted by the display part DP1′ iszero or very small. Further, in the display part DP1′, as compared withthe display part DP1, the visual effect caused by the second opticaleffect layer 17 is slightly obscure. As the result thereof, when theabove-mentioned structure is adopted, the brightness and color can bedifferentiated between the display part DP1 and the display part DP1′.

In the display 10 shown in FIG. 14, the reflective material layer 13covers only a part of the second interface part IF2. And, the secondoptical effect layer 17 has a portion that faces the first opticaleffect layer 12 at both positions of a portion of the second interfacepart IF2 that is covered with the reflective material layer 13 and aportion of the second interface part IF2 that is not covered with thereflective material layer 13.

In the display part DP2′, the second interface part IF2 is not coveredwith the reflective material layer 13. Accordingly, the display partDP2′ offers a visual effect almost the same as that offered in the casewhere the first interface part IF2 does not exist. That is, theintensity of the diffracted light emitted by a portion of the secondinterface part IF2 that is not covered with the reflective materiallayer 13 is zero or very small. Therefore, the intensity of thediffracted light is far lower than that of a light emitted by thecorresponding portion of the second optical effect layer 17.Accordingly, the display part DP2′ is usually observed as a region thatexhibits the visual effect caused by the second optical effect layer 17.As the result thereof, when the above-mentioned structure is adopted,the brightness and color can be differentiated between the display partDP2 and the display part DP2′.

In the display 10 shown in FIG. 14, the reflective material layer 13covers only a part of the third interface part IF3. And, the secondoptical effect layer 17 has a portion that faces the first opticaleffect layer 12 at both positions of a portion of the third interfacepart IF3 that is covered with the reflective material layer 13 and aportion of the third interface part IF3 that is not covered with thereflective material layer 13.

In the display part DP3′, the third interface part IF3 is not coveredwith the reflective material layer 13. Accordingly, the intensity of thediffracted light emitted by a portion of the third interface part IF3that is not covered with the reflective material layer 13 is zero orvery small. That is, the intensity of the reflected light is far lowerthan that of a light emitted by the corresponding portion of the secondoptical effect layer 17. Accordingly, the display part DP3′ is usuallyobserved as a region that exhibits the visual effect caused by thesecond optical effect layer 17. As the result thereof, when theabove-mentioned structure is adopted, the brightness and color can bedifferentiated between the display part DP3 and the display part DP3′.

As above, when at least one of the interface parts IF1 to IF3 includes aportion that is covered with the reflective material layer 13 and aportion that is not covered with the reflective material layer 13, morecomplicated optical effects can be achieved. That is, when implementedlike this, still higher forgery inhibition effects can be achieved.

In the display 10 shown in FIG. 14, the reflective material layer 13covers only a part of a main surface of the first optical effect layer12. Such a reflective material layer 13 can be formed as describedbelow.

According to a first method, on one main surface of the first opticaleffect layer 12, a water-based ink is printed in a negative pattern. Alayer of a reflective material is formed over an entire surface thereofby use of an evaporation method or a sputtering method. Then, thewater-based ink is washed away with water. Thus, a portion of the layerof the reflective material that is located above the pattern of thewater-based ink is removed. The reflective material layer 13 that coversonly a part of one main surface of the first optical effect layer 12 isthus obtained.

According to a second method, firstly, on an entirety of one mainsurface of the first optical effect layer 12, a layer of a reflectivematerial is formed. Thereafter, a masking agent is printed on the layerin a positive pattern. Then, by use of a corrosive agent, a portion ofthe layer of the reflective material that is not covered with themasking agent is removed. Subsequently, as required, the masking agentis removed. The reflective material layer 13 that covers only a part ofone main surface of the first optical effect layer 12 is thus obtained.

According to a third method, firstly, on an entirety of one main surfaceof the first optical effect layer 12, a layer of the reflective materialis formed. Thereafter, a portion of the layer of the reflective materialthat is to be removed is illuminated with high-intensity laser beam.Thereby, a part of the layer of the reflective material is selectivelydestroyed. The reflective material layer 13 that covers only a part ofone main surface of the first optical effect layer 12 is thus obtained.

FIG. 15 is a sectional view schematically showing a display according toanother modification. A display 10 shown in FIG. 15 has a structuresimilar to the display shown in FIG. 14, except that a first opticaleffect layer 12 has light-transmitting properties and is furtherprovided with a light-transmitting substrate 21, a light-absorbing layer23, and an adhesive layer 25.

As the light-transmitting substrate 21, for examples, what has thelight-transmitting properties of the above-described substrates 11 isused. The light-transmitting substrate 21 is typically transparent. Thelight-transmitting substrate 21 may be omitted.

The light-absorbing layer 23 faces the second optical effect layer 17with the first optical effect layer 12 interposed therebetween. As thelight-absorbing layer 23, a layer of, for example, a black ink is used.The term “black” here means that, for example, when the display 10 isilluminated with light in the normal direction and the intensity of theregularly reflected light is measured, the reflectance of all lightcomponents in the range of 400 nm to 700 nm of wavelength is 10% orless.

Alternatively, as the light-absorbing layer 23, a magnetic layer may beadopted. That is, the light-absorbing layer 23 may contain a magneticsubstance. The magnetic substance is contained in the light-absorbinglayer 23 typically in a form of powder. Examples of the powder ofmagnetic substances include iron oxide powder, chromium oxide powder,cobalt powder, ferrite powder and mixtures thereof. Further, in thiscase, the light-absorbing layer 23 may further contain a black pigmentsuch as carbon black or the like. As the powder of the magneticsubstance that the light-absorbing layer 23 can contain, iron oxidepowder is preferable and magnetite powder is particularly preferable.Further, when the light-absorbing layer 23 contains the powder of themagnetic substance, the light-absorbing layer 23 typically furthercontains a transparent binder.

When the magnetic layer is adopted as the light-absorbing layer 23, inaddition to the authenticity check based on the optical properties ofthe display 10, also the authenticity check based on the magneticproperties can be conducted. That is, when implemented like this, theforgery prevention effect of the display 10 can be further improved.

In FIG. 15, a case where the light-absorbing layer 23 faces the secondoptical effect layer 17 with the first optical effect layer 12interposed therebetween is depicted. However, a position of thelight-absorbing layer 23 is not restricted thereto. For example, thelight-absorbing layer 23 may be interposed between the first opticaleffect layer 12 and the second optical effect layer 17. When thelight-absorbing layer 23 is interposed between the first optical effectlayer 12 and the second optical effect layer 17, the first opticaleffect layer 12 may not have light-transmitting properties.

Although FIG. 15 shows the case where the light-absorbing layer 23 facesan entirety of the second optical effect layer 17 with the first opticaleffect layer 12 interposed therebetween, a configuration of thelight-absorbing layer 23 is not restricted thereto. That is, thelight-absorbing layer 23 may face the second optical effect layer 17 ata position of a portion of the first interface part IF1 that is notcovered with the reflective material layer 13 with the first opticaleffect layer 12 interposed therebetween. Alternatively, thelight-absorbing layer 23 may be interposed between the first opticaleffect layer 12 and the second optical effect layer 17 at a position ofa portion of the first interface part IF1 that is not covered with thereflective material layer 13.

An adhesive layer 25 is interposed between the light-absorbing layer 23and the substrate 11, and bonding them together. As the material of theadhesive layer 25, known materials can be used. The adhesive layer 25may be omitted.

The display part DP1′ of the display 10 shown in FIG. 15 includes thelight-absorbing layer 23. The light-absorbing layer 23 absorbs lighttransmitted through the second optical effect layer 17. Accordingly, inthis case, in the display part DP1′, the visual effect caused by thesecond optical effect layer 17 can be clearly recognized.

The display parts DP2′ and DP3′ of the display 10 shown in FIG. 15includes the light-absorbing layer 23. The light-absorbing layer 23absorbs light transmitted through the second optical effect layer 17.Accordingly, in the display parts DP2′ and DP3′, the visual effectcaused by the second optical effect layer 17 can be clearly recognized.

Accordingly, when the incident angle of the illumination light and theobservation angle is narrow, the display part DP1, the display partDP1′, the display part DP2′ and the display part DP3′ are observed asregions that exhibit almost the same optical effect. However, when theincident angle of the illumination light and the observation angle arewide, as described for the display 10 shown in FIG. 14, the diffractedlight having relatively high intensity is observed at the display partDP1. On the other hand, in this case, the display parts DP1′ to DP3′ donot emit such diffracted light. Accordingly, in this case, by combiningthe display part DP1 and the display parts DP1′ to DP3′, a latent imagecan be formed.

The display 10 described above may be used as, for example, an adhesivelabel such as a sealing label or the like, a transfer foil such as astripe transfer foil, a spot transfer foil or the like, or a part ofthread. Alternatively, the display 10 may be used as a part of teartape.

FIG. 16 is a sectional view schematically showing an adhesive labelaccording to an embodiment of the present invention. A adhesive label100 shown in FIG. 16 includes the display 10 shown in FIGS. 1 and 2 anda sticky layer 30 provided on the display 10.

The sticky layer 30 is disposed on one of main surfaces of the substrate11 that is on a side opposite to the second optical effect layer 17. Thesticky layer 30 faces the second optical effect layer 17 with the firstoptical effect layer 12 and the reflective material layer 13 interposedtherebetween. As a material of the sticky layer 30, for example, apressure-sensitive adhesive is used. The sticky layer 30 is formed byapplying a mixture of the adhesive and a solvent by a method such asgravure coating, roll coating, screen coating, blade coating or thelike. A thickness of the sticky layer 30 is in the range of, forexample, 1 μm to 10 μm.

The adhesive label 100 is adhered to, for example, an article of whichauthenticity should be confirmed, or, other article such as a substrateof a tag to be attached to such an article. Thereby, the forgeryprevention effect can be imparted to the article.

A brittle layer may further disposed between the display 10 and thesticky layer 30 so as impart an upholstery prevention effect to theadhesive label 100. In this case, higher forgery prevention effect canbe achieved.

FIG. 17 is a sectional view schematically showing a transfer foilaccording to an embodiment of the invention. A transfer foil 200 shownin FIG. 17 includes the display 10 shown in FIGS. 1 and 2, and a supportlayer 45 releasably supporting the display 10. FIG. 17 shows, as anexample, a case where a release layer 43 is disposed between the secondoptical effect layer 17 and the support layer 45 and an adhesive layer41 is disposed on one of the main surfaces of the substrate 11 that ison a side opposite to the second optical effect layer 17.

The support layer 45 is a film or sheet of, for example, a resin. As thematerials of the support layer 45, for example, polyethyleneterephthalate resin, polyethylene naphthalate resin, polyimide resin,polyethylene resin, polypropylene resin or vinyl chloride resin is used.

The release layer 43 plays a role in making the release of the supportlayer 45 easy when the transfer foil 200 is transferred on atransfer-receiver. As the material of the release layer 43, for example,resins mentioned above as the materials for the relief structure-forminglayer 110 are used. The release layer 43 may further contain an additivesuch as paraffin wax, carnauba wax, polyethylene wax, silicone or thelike. A thickness of the release layer 43 is set in the range of, forexample, 0.5 μm to 5 μm.

Examples of the materials of the adhesive layer 41 include a reactivecuring adhesive, a solvent evaporation-type adhesive, a hot-meltadhesive, an EB-curable adhesive, a heat-sensitive adhesive and so on.

Examples of the reactive curing adhesives include polyurethane resinssuch as polyester urethane, polyether urethane, acryl urethane and soon, or epoxy resins.

Examples of the solvent evaporation-type adhesives include aqueousemulsion adhesives containing vinyl acetate resin, acrylic acid estercopolymer resin, ethylene-vinyl acetate copolymer resin, ionomer resin,urethane resin or the like, and latex adhesives containing naturalrubber, styrene-butadiene copolymer resin, acrylonitrile-butadienecopolymer resin or the like.

Examples of the hot-melt adhesives include adhesives that containethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylatecopolymer resin, polyester resin, polycarbonate resin, polyvinyl etherresin, polyurethane resin or the like as a base resin.

As the EB-curable adhesive, for example, adhesives containing anoligomer having one or a plurality of vinyl functional groups such asacryloyl group, allyl group, vinyl group and so on as a main componentare used. For example, as the EB-curable adhesive, a mixture ofpolyester acrylate, polyester methacrylate, epoxy acrylate, epoxymethacrylate, urethane acrylate, urethane methacrylate, polyetheracrylate or polyether methacrylate and a tackifier can be used. Examplesof the tackifiers include acrylates containing phosphorus or derivativesthereof, or, acrylates containing carboxyl group or derivatives thereof.

As the heat-sensitive adhesives, for example, polyester resin, acrylresin, vinyl chloride resin, polyamide resin, polyvinyl acetate resin,rubber-based resin, ethylene-vinyl acetate copolymer resin or vinylchloride-vinyl acetate copolymer resin is used.

The adhesive layer 41 can be obtained, for example, by coating thesubstrate 11 with the above-mentioned resin by use of a coater such as agravure coater, a micro-gravure coater, a roll coater or the like.

The transfer foil 200 can be transferred onto a transfer-receiver by,for example, a roller transfer machine or a hot stamper. At this time,delamination occurs at the protective release layer 43 and the display10 is attached via the adhesive layer 41 to the transfer-receiver.

As described above, the display 10 offers an excellent forgeryprevention effect. Accordingly, when the display 10 is supported by anarticle, also the labeled article, which is an authentic article, isdifficult to forge. Further, since the display 10 offers theabove-described visual effect, whether an article whose authenticity isunknown can be readily discriminated between a authentic article and anon-authentic article.

FIG. 18 is a plan view schematically showing an example of a labeledarticle. FIG. 19 is a sectional view taken along a XIX-XIX line of thelabeled article shown in FIG. 18. FIGS. 18 and 19 show a printed matter300 as an example of a labeled article. The printed matter 300 is a giftcertificate and contains a printed matter body 60.

The printed matter body 60 includes a substrate 61. The substrate 61 isa paper in which at least a portion corresponding to the display 10 hasthe light-transmitting properties. On the substrate 61, a printed layer61 is formed. On a surface of the substrate 61 on which the printedlayer 61 is formed, the display 10 is fixed. The display 10 is fixed onthe substrate 61 by bonding them together via, for example, a stickylayer or an adhesive layer.

Since the printed matter 300 contains the display 10, it is difficult toforge the printed matter 300. Further, since the printed matter 300contains the display 10, it is easy to discriminate an article whoseauthenticity is unknown between an authentic article or a non-authenticarticle.

The display 10 contained in the printed matter 300 shown in FIGS. 18 and19 has the same configuration as that of the display 10 shown in FIGS. 1and 2 except the following points. Firstly, in the display 10 that theprinted matter 300 shown in FIGS. 18 and 19 includes, the substrate 11is omitted. Further, in the display 10, the second optical effect layer17 faces the reflective material layer 13 with the first optical effectlayer 12 interposed therebetween. Then, in the display 10, thelight-transmitting layer 15 is disposed between the reflective materiallayer 13 and the substrate 61. In addition, in the display 10,configurations of an interface part disposed on one main surface of thefirst optical effect layer 12 and the reflective material layer 13covering these are different from those of the displays 10 shown inFIGS. 1 and 2.

The first optical effect layer 12 contained in the printed matter 300shown in FIGS. 18 and 19 contains, as a first interface part IF1, afirst sub-region IF1A and a second sub-region IF1B. FIGS. 18 and 19depict, as an example, a case where the first sub-region IF1A and thesecond sub-region IF1B are adjacently located. Hereinafter, a portion ofthe display 10 that corresponds to the first sub-region IF1A is referredto as a display part DP1A. Further, a portion of the display 10 thatcorresponds to the first sub-region IF1B is referred to as a displaypart DP1B.

In the first sub-region IF1A and the second sub-region IF1B, the minimumcenter-to-center distances of the recesses or protrusions 14 b aredifferent from each other. Here, as an example, it is assumed that theminimum center-to-center distance of the recesses or protrusions 14 bdisposed in the first sub-region IF1A is 300 nm, and the minimumcenter-to-center distance of the recesses or protrusions 14 b disposedin the second sub-region IF1B is 400 nm.

As described above, the first interface part IF1 has a smallreflectance. The difference between the reflectances of the firstsub-region IF1A and the second sub-region IF1B is relatively small.Accordingly, when an absolute value of the incident angle of theillumination light is relatively small, for example, when the absolutevalue of the incident angle is less than 60°, in both of the firstsub-region IF1A and the second sub-region IF1B, the optical effect dueto the second optical effect layer 17 can be very clearly observed.Accordingly, in this case, the display part DP1A and the display partDP1B can not be differentiated from each other, or, are very difficultto differentiate from each other.

On the other hand, when the absolute value of the incident angle of theillumination light is relatively large, for example, the absolute valueof the incident angle is 60° or more and less than 90°, each of thefirst sub-region IF1A and the second sub-region IF1B emits a diffractedlight having an wavelength different from each other. For example, whenthe absolute value of the incident angle is in the range of from 60° to70° and the absolute value of the observation angle is in the range offrom 60° to 70°, the display part DP1A is observed as a region of greencolor, and the display part DP1B is observed as a region of red color.That is, when the absolute value of the incident light of theillumination light is relatively large, the display part DP1A and thedisplay part DP1B can be differentiated from each other.

That is, when the configuration like this is adopted, a combination ofthe display part DP1A and the display part DP1B can form a latent image.Accordingly, by implementing like this, the forgery prevention effect ofthe display 10 and the printed matter 300 can be further enhanced.

In FIGS. 18 and 19, a voucher is exemplified as the printed matter 300including the display 10. However, the printed matter including thedisplay 10 is not restricted thereto. For example, the printed matterincluding the display 10 may be other securities such as stockcertificates and so on.

Alternatively, the printed matter including the display 10 may be a cardsuch as an ID (identification) card, a magnetic card, a wireless card,an IC (integrated circuit) card or the like. Alternatively, the printedmatter including the display 10 may be a tag to be attached to anarticle whose authenticity should be confirmed. Alternatively, theprinted matter including the display 10 may be a package housing anarticle whose authenticity should be confirmed or a part thereof. Inthis case, as a material of the substrate 61, for example, plastichaving light-transmitting properties is used.

In the printed matter 300 shown in FIGS. 18 and 19, the display 10 isstuck to the substrate 61. However, the display 10 may be supported bythe substrate 61 according to other method.

For example, when a paper is used as the substrate 61, the display 10may be buried in the paper. In this case, for example, the display 10may be paper made inside of the paper.

When the configuration like this is adopted, the display 10 is formed,typically, into a thread form. On one main surface of the display 10processed into a thread form, typically, a hot melt adhesive is applied.

The display 10 is buried inside of the paper, for example, as follows.

Firstly, a paper stock containing cellulose fibers and a dispersant isprepared. Then, using a twin cylinder paper machine, the paper stock ismade into two wet fiber layers. Then, the two fiber layers are overlaidon top of another, and at this time, the display 10 is sent between thefiber layers. Thereafter, a laminate including the two fiber layers andthe display 10 interposed therebetween is dried. Then, as required, acutting operation is conducted. In a manner like this, a paper havingthe display 10 buried therein is obtained.

Alternatively, a process where the display 10 is buried inside of thepaper may be conducted also as follows.

For example, the display 10 may be buried using a Foudrinier papermachine. Specifically, firstly, into a flow of the paper stock of thecellulose fibers and a dispersant, the display 10 dispersed in adispersion medium is introduced via a nozzle. Thus, the display 10 isburied in a paper web formed on a paper-making net. Thereafter, this isdried. Then, as required, this is cut. Thus, a paper having the display10 buried therein is obtained.

When a paper is used as the substrate 61, a part of the paper thatcorresponds to the display 10 may be opened entirely or partially.

FIG. 20 is a plan view schematically showing another example of alabeled article. FIG. 21 is a sectional view taken along a XXI-XXI lineof the labeled article shown in FIG. 20.

The display 10 that the printed matter 300 shown in FIGS. 20 and 21contains has the configuration as that of the display shown in FIG. 15except that the substrate 11 is omitted and configurations of aninterface part and the reflective material layer 13 disposed on one mainsurface of the first optical effect layer 12 are different.

A labeled article shown in FIGS. 20 and 21 is a printed matter 300, andthe substrate 61 thereof is a paper. Inside of the paper, the display 10is buried. In addition, a part of the paper that corresponds to thedisplay 10, apertures AP are disposed. That is, in each of the aperturesAP, the display 10 is partially exposed to the outside. When theconfiguration like this is adopted, the display 10 is difficult todetach from the substrate 61. In addition, at a position where theapertures AP is disposed, an influence of the light scattering propertyof the paper on the optical characteristics of the display 10 can besuppressed to the minimum level.

The printed matter 300 shown in FIGS. 20 and 21 includes a display partDP1, a display part DP2, a display part DP3, and a display part DP3′.

As described above, the reflectance of the first interface part IF1 issmall. Further, the display part DP3′ does not include the reflectivematerial layer 13 and includes the light-absorbing layer 23.Accordingly, when the absolute value of the incident angle of theillumination light is relatively small, for example, the absolute valueof the incident angle is less than 60°, in both of the display part DP1and the display part DP3′, the optical effect caused by the secondoptical effect layer 17 can be very clearly observed. Accordingly, inthis case, the display part DP1 and the display part DP3′ can not bedifferentiated from each other or can be differentiated from each otherwith difficulty.

On the other hand, when the absolute value of the incident angle of theillumination light is relatively large, for example, the absolute valueof the incident angle is 60° or more and less than 90°, only the displaypart DP1 of the display part DP1 and the display part DP3′ displays acolor corresponding to the diffracted light. That is, when the absolutevalue of the incident angle of the illumination light is relativelylarge, the display part DP1 and the display part DP3′ can bedifferentiated from each other.

Namely, when the above configuration is adopted, a combination of thedisplay part DP1 and the display part DP3′ can form a latent image.Accordingly, when implemented like this, the forgery prevention effectof the display 10 and the printed matter 300 can be further enhanced.

As the material of the substrate 61, materials other than paper may beused. For example, as the material, a resin that has light-transmittingproperties at least at a portion corresponding to the display 10 may beused. In this case, the display 10 may be buried inside of the substrate61. Alternatively, when the light scattering property of the substrate61 is small at least at a portion corresponds to the display 10, forexample, when this portion is transparent, the display 10 may be fixedon a back surface of the substrate 61, that is, on a surface on a sideopposite to a surface where a printed layer 61 is disposed.

The labeled article may not be a printed matter. That is, the display 10may be supported by an article that does not contain a printed layer.

The display 10 may be used for purposes other than forgery prevention.For example, the display 10 may be used also as toys, learningmaterials, or ornaments.

EXAMPLES Example 1

Firstly, as a support layer 45, a biaxially stretched PET film (PETFILM; E5100, manufactured by TOYOBO Co., Ltd.) having a thickness of 12μm was prepared. Further, an ink having the following composition wasprepared. This ink is referred to as an “ink 1”.

Photopolymerizable nematic liquid crystal (PARIOCOLOR LC242,manufactured by BASF): 100 parts by mass

Chiral agent (PARIOCOLOR LC756, manufactured by BASF): 4.8 parts by mass

Polymerization initiator (IRGACURE 369, manufactured by Chiba SpecialtyChemicals): 5 parts by mass

Solvent (methyl ethyl ketone): 200 parts by mass

Then, the ink 1 was applied to the biaxially stretched polyester film ata thickness of 5 μm. This was dried in a drying furnace at 120° C. toalign liquid crystal molecules. Subsequently, in this state, using ahigh-pressure mercury vapor lamp of 120 W/cm, it was illuminated at 500mJ/cm². Thus, a layer containing a cholesteric liquid crystal was curedand thereby a second optical effect layer 17 was obtained.

In the next place, an ink having the following composition was prepared.The ink is referred to as an “ink 2”.

Two-component urethane ink (K448, manufactured by Toyo Ink Co., Ltd.):100 parts by mass

Isocyanate curing agent (UR100B, manufacture by Toyo Ink Co., Ltd.): 10parts by mass

Solvent (methyl ethyl ketone): 10 parts by mass

Next, the ink 2 was applied by gravure coating on a second opticaleffect layer 17 at a thickness of 2 μm. After drying this, an agingprocess was applied at 40° C. for 3 days. Thus, a layer of a resin wasobtained.

Subsequently, a nickel electrotype provided with a recess and/orprotrusion structure was prepared. On the nickel electrotype, firstly, aregion of a plurality of protrusions arranged two-dimensionally at aspatial frequency of 3000 lines/mm and individually having aforward-tapered shape was formed. Further, on the nickel electrotype, inthe second place, 3 regions of grooves having spatial frequencies of 500lines/mm, 1,000 lines/mm and 1,500 lines/mm were formed. The nickelelectrotype was installed on a cylinder roll, and a hot-press embossingprocess was conducted against the layer of the resin. Thus, a firstoptical effect layer 12 provided with a first interface part IF1 and asecond interface part IF2 was obtained.

Thereafter, on a main surface of the first optical effect layer 12 wherethe interface parts IF1 and IF2 were disposed, by use of a vacuumevaporation method, aluminum was deposited. In such a manner, areflective material layer 13 having a thickness of 500 Å was obtained.

Subsequently, a reactive curing adhesive as an ink having the followingcomposition was prepared. Hereinafter, the ink is referred to as an “ink3”.

Polyester resin (VYLON 240, manufactured by Toyobo Co., Ltd.): 100 partsby mass

Block isocyanate (TPA-B80X, manufactured by Asahi Kasei Chemicals): 2parts by mass

Solvent (toluene): 100 parts by mass

Solvent (methyl ethyl ketone): 100 parts by mass

The reactive curing adhesive as the ink 3 was applied on the reflectivematerial layer 13 by micro-gravure method at a thickness of about 10 μm.In such a manner, an adhesive layer 41 was obtained.

As described above, a transfer foil 200 with a display 10 was produced.The transfer foil 200 was pressed against a printed form of a giftcertificate under heating at 160° C. for 10 second. Then, a PET film asa support layer 45 was peeled therefrom. Thus, a printed matter on whichthe display 10 was transferred was obtained.

Example 2

An ink having the following composition was prepared. Hereinafter, theink is referred to as an “ink 4”.

Vinyl chloride-vinyl acetate copolymer resin (SOLBIN A, manufactured byNissin Chemical Industry Co., Ltd.): 100 parts by mass

Cholesteric liquid crystal powder (HELICONE HC, SLM 90120, manufacturedby LCP Technologies): 30 parts by mass

Solvent (toluene): 250 parts by mass

Solvent (methyl ethyl ketone): 250 parts by mass

Then, a printed matter 300 including a display 10 was produced in thesame manner as in Example 1 except that the ink 4 was used in place ofthe ink 1.

Example 3

As a second optical effect layer 17, a coextrusion multilayer film(TEIJIN TETRON FILM, MLF-13.0, manufactured by Teijin-DuPont Co., Ltd.)was prepared. Then, on the second optical effect layer 17, an ink 2 wasapplied by gravure method at a thickness of 2 This was dried and aged at40° C. over 3 days. Thus, a layer of a resin was obtained.

The nickel electrotype was installed on a cylinder roll, and anembossing process was applied under heating and pressure on the layer ofresin. In such a manner, a first optical effect layer 12 provided with afirst interface part IF1 and a second interface part IF2 was obtained.

Thereafter, on a main surface of the first optical effect layer 12 wherethe interface parts IF1 and IF2 were disposed, aluminum was depositedusing vacuum evaporation. In such a manner, a reflective material layer13 having a thickness of 500 Å was obtained.

Subsequently, using micro-gravure method, a reactive curing adhesive asan ink 3 was applied on the reflective material layer 13 at a thicknessof about 10 μm. In such a manner, a sticky layer 30 was obtained.

Then, the resulted laminate was punched with a predetermined cutter.Thus, an adhesive label 100 with a display 10 was produced. The adhesivelabel 100 was attached under heating and pressure on a printed form of agift certificate under condition of 160° C. for 10 sec. Thus, a printedmatter 300 having a display 10 attached thereon was obtained.

Example 4

An ink having the following composition was prepared. Hereinafter, theink is referred to as an “ink 5”.

Vinyl chloride-vinyl acetate copolymer resin (SOLBIN A, manufactured byNissin Chemical Industry Co., Ltd.): 100 parts by mass

Pearl pigment powder (IRIODIN 231, manufactured by Merck): 30 parts bymass

Solvent (toluene): 250 parts by mass

Solvent (methyl ethyl ketone): 250 parts by mass

Then, a printed matter 300 including a display 10 was produced in thesame manner as that in Example 1 except that the ink 5 was used in placeof the ink 1.

Example 5 Comparative Example

A printed matter including a display was produced in the same manner asin Example 1 except that a resin layer was formed in place of a firstoptical effect layer 12 by an embossing process including application ofheat and pressure using a nickel electrotype which was provided withthree regions including grooves arranged at spatial frequencies of 500lines/mm, 1,000 lines/mm and 1,500 lines/mm.

Example 6 Comparative Example

Firstly, a layer containing a cholesteric liquid crystal was formed on abiaxially stretched PET film as a support layer in the same manner asthat described in Example 1.

Then, on the layer containing the cholesteric liquid crystal, aluminumwas deposited by vacuum evaporation. In such a manner, on the layercontaining the cholesteric liquid crystal, a metal layer having athickness of 500 Å was formed.

Subsequently, a mask ink having the following composition was prepared.Hereinafter, the ink is referred to as an “ink 6”.

Vinyl chloride-vinyl acetate copolymer resin (SOLBIN A, manufactured byNissin Chemical Industry Co., Ltd.): 100 parts by mass

Polyethylene wax (ADDITIVE 180, manufactured by Toyo Ink Co., Ltd.): 10parts by mass

Solvent (methyl ethyl ketone): 300 parts by mass

On the metal layer, the ink 6 was pattern-printed by gravure method at athickness of 2 μm.

Thereafter, the resulting laminate was dipped in an aqueous solution of2% by mass sodium hydroxide at 50° C. over 5 sec. In such a manner, aportion of the metal layer that was covered with a mask layer wasremoved.

Subsequently, as a light-absorbing magnetic ink, an ink having thefollowing composition was prepared. Hereinafter, the ink is referred toas an “ink 7”.

Vinyl chloride-vinyl acetate copolymer resin (SOLBIN A, manufactured byNissin Chemical Industry Co., Ltd.): 50 parts by mass

Powder of magnetic substance (JEM-H, manufactured by MitsubishiMaterials Electronic Chemicals Co., Ltd.): 50 parts by mass

Dispersant (DISPERBYK-106, manufactured by BYK Chemie): 3 parts by mass

Isocyanate curing agent (UR100B, manufactured by Toyo Ink Co., Ltd.): 30parts by mass

Solvent (methyl ethyl ketone): 300 parts by mass

The ink 7 was applied at a thickness of 4 μm on an entire surface of themetal layer and the resin layer by gravure coating. After drying this,aging was conducted at 60° C. for 7 days. In such a manner, alight-absorbing layer was formed.

On the light-absorbing layer, a reactive curing adhesive of an ink 3 wasapplied at a thickness of about 10 μm by micro-gravure. In such amanner, a transfer foil was obtained.

The transfer foil was pressed under heating against a printed form ofgift certificate at 160° C. for 10 sec. Then, a PET film as a supportlayer was peeled therefrom. Thus, a printed matter including a displaywas obtained.

Example 7 Comparative Example

A laminate of a PET film as a support layer, a layer containing acholesteric liquid crystal, and an embossed resin layer was produced inthe same manner as that described in Example 5.

Next, on an embossed main surface of the resin layer, aluminum wasdeposited by vacuum evaporation. In such a manner, on the layercontaining a cholesteric liquid crystal, a metal layer having athickness of 500 Å was formed.

On the metal layer, an ink 6 was pattern printed by gravure coating at athickness of 2 μm. Thus, a mask layer was obtained.

Thereafter, the resulting laminate was dipped in an aqueous solution of2% by mass sodium hydroxide at 50° C. for 5 sec. In such a manner, aportion of the metal layer covered with the mask layer was removed.

Then, an ink 7 was applied on entire surfaces of the metal layer and theresin layer by gravure coating at a thickness of 4 μm. After dryingthis, an aging process was conducted at 60° C. for 7 days. In such amanner, a light-absorbing layer was formed.

On the light-absorbing layer, a reactive curing adhesive as an ink 3 wasapplied at a thickness of about 10 μm by micro-gravure coating. In sucha manner, a transfer foil was obtained.

The transfer foil was pressed under heating against a printed form of agift certificate at 160° C. for 10 sec. Then, a PET film as a supportlayer was peeled therefrom. Thus, a printed matter including a displaywas obtained.

Example 8 Comparative Example

As a support layer, a biaxially stretched film (PET FILM; E5100,manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm wasprepared. Further, a hologram ink having the following composition wasprepared. Hereinafter, the ink is referred to as an “ink 8”.

Holographic powder (HOLOGRAM INK #256, manufactured by Jujo ChemicalCo., Ltd.): 20 parts by mass

Acrylic resin (BR60, manufactured by Mitsubishi Rayon Co., Ltd.): 100parts by mass

Solvent (toluene): 200 parts by mass

Solvent (methyl ethyl ketone): 200 parts by mass

The ink 8 was applied on the PET film at a thickness of 3 μm. Afterdrying the resulting coating, an aging process was applied at 60° C. for5 days to cure. In such a manner, a layer of holographic powder wasformed.

On the layer of holographic powder, an ink 2 was applied by gravurecoating at a thickness of 2 μm. After drying this, an aging process wasconducted at 40° C. for 3 days. In such a manner, a resin layer wasformed.

Then, using the same nickel electrotype as that used in Example 1, anembossing process was performed on one main surface of the resin layer.On the embossed main surface of the resin layer, aluminum was depositedby vacuum evaporation. In such a manner, on a layer containing acholesteric liquid crystal, a metal layer having a thickness of 500 Åwas formed.

Subsequently, on the metal layer, a reactive curing adhesive as an ink 3was applied by micro-gravure coating at a thickness of about 10 μm. Insuch a manner, a transfer foil was obtained.

The transfer foil was pressed against a printed form of a giftcertificate under heating at 160° C. for 10 sec. Then, a PET film as asupport layer was peeled therefrom. Thereby, a printed matter includinga display was obtained.

<Evaluation>

For each of the printed matters according to Examples 1 to 8, thefollowing items were evaluated. These evaluation results are summarizedin Table 1 below.

(Patterning Characteristics)

The printed matter was observed from a direction normal to a mainsurface of the display, and was evaluated whether or not it gave anappearance having a print pattern. The evaluation was conducted based onthe following criteria.

S: A case where the pattern was very clearly observed.

A: A case where the pattern was clearly observed.

C: A case where the pattern was not observed.

(Positional Accuracy)

Evaluated was whether or not a position of a pattern corresponding tothe recess structure and/or the protrusion structure provided on thefirst optical effect layer or the resin layer coincided with a positionof a pattern visually recognized when the printed matter was observedfrom a direction normal to a main surface of the display. The evaluationwas conducted based on the following criteria.

A: A case where positions of the patterns coincided.

C: A case where positions of the patterns did not coincide.

(Patterning Accuracy)

Evaluated was whether or not a pattern such as fine design and charactercould be displayed when the printed matter was observed from a directionnormal to a main surface of the display. The evaluation was conductedbased on the following criteria.

A: A case where a pattern such as fine design and character could bedisplayed.

C: A case where a pattern such as fine design and character could not bedisplayed.

(Overt Visibility)

Whether or not the authenticity check could be performed without usingan instrument or device was evaluated. The evaluation was performedbased on the following criteria.

A: A case where the authenticity check could be readily performedwithout using an instrument or device.

B: A case where the authenticity check could be performed without usingan instrument or device.

C: A case where the authenticity check could not be performed withoutusing an instrument or device.

(Wavelength Selectivity)

Evaluated was whether or not only a light having a specific wavelengthcould be selectively perceived when observed at a specific observationangle. The evaluation was performed based on the following criteria.

A: A case where only a light having a specific wavelength could beselectively perceived when observed at a specific observation angle.

C: A case where it was impossible that only a light having a specificwavelength was selectively perceived when observed at a specificobservation angle.

(Polarization Change)

Evaluated was whether or not the polarization property changed fromcircular polarization to linear polarization when a direction from whichthe display was observed was gradually changed from the direction normalto a main surface of the display toward the wide angle side. Theevaluation was performed based on the following criteria.

A: A case where the polarization property changed.

C: A case where the polarization property did not change.

(Cost)

The cost necessary for producing a printed matter was evaluated. Theevaluation was performed based on the following criteria.

S: A case where production cost was low.

A: A case where production cost was slightly low.

C: A case where production cost was slightly high.

(Crack Resistance)

The crack resistance of a display was evaluated by use of an NBScrumpling device (manufactured by IGT Testing System) used in thecrumpling test for banknotes.

A: A case where appearance change was hardly found.

B: A case where a few cracks were found.

C: A case where a lot of cracks were found.

TABLE 1 Patterning Positional Patterning Overt Wavelength PolarizationCrack Example characteri accuracy accuracy visibility selectivit changeCost resistance 1 S A A A A A A B 2 A A A B-A A A A B 3 A A A B-A A C SA 4 A A A B-A C C A B 5 C — — C C C A B 6 A C C A A C C B 7 A C C C-A CC C B 8 C — — C-A C C A B

As is obvious from Table 1, in Examples 1 to 4, high forgery preventioneffect could be achieved.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventionconcept as defined by the appended claims and their equivalents.

LIST OF REFERENCE SYMBOLS

-   10 . . . Display-   11 . . . Substrate-   12 . . . First optical effect layer-   13 . . . Reflective material layer-   14 a . . . Groove-   14 b . . . Recess or protrusion-   15 . . . Light-transmitting layer-   17 . . . Second optical effect layer-   21 . . . Light-transmitting substrate-   23 . . . Light-absorbing layer-   25 . . . Adhesive layer-   30 . . . Sticky layer-   31 a . . . Illumination light-   31 b . . . Illumination light-   31 c . . . illumination light-   32 a . . . Regularly reflected light-   32 b . . . Regularly reflected light-   32 c . . . Regularly reflected light-   33 a . . . 1st-order diffracted light-   33 b . . . 1st-order diffracted light-   41 . . . Adhesive layer-   43 . . . Release layer-   45 . . . Support layer-   60 . . . Printed matter body-   61 . . . Substrate-   62 . . . Print layer-   100 . . . Adhesive label-   200 . . . Transfer foil-   300 . . . Printed matter-   AP . . . Aperture-   DP1 . . . Display part-   DP1′ . . . Display part-   DP1A . . . Display part-   DP1B . . . Display part-   DP2 . . . Display part-   DP2′ . . . Display part-   DP3 . . . Display part-   DP3′ . . . Display part-   IF1 . . . First interface part-   IF2 . . . Second interface part-   IF3 . . . Third interface part

What is claimed is:
 1. A display comprising: a first optical effect layer including a first interface part, the first interface part being provided with recesses or protrusions arranged two-dimensionally at the minimum center-to-center distance in a range of 200 nm to 500 nm, each of the recesses or protrusions having a forward-tapered shape; a reflective material layer covering at least a part of the first interface part; and a second optical effect layer including, at a position of a first portion of the first interface part that is covered with the reflective material layer, a portion that faces the reflective material layer with the first optical effect layer interposed therebetween or faces the first optical effect layer with the reflective material layer interposed therebetween, the second optical effect layer containing at least one of a cholesteric liquid crystal, a pearl pigment and a multilayer interference film, wherein the first optical effect layer further includes a second interface part that is adjacent to the first interface part and provided with grooves disposed one-dimensionally at the minimum center-to-center distance larger than the minimum center-to-center distance of the recesses or protrusions, and a third interface part as a flat surface that is adjacent to the first interface part, wherein the reflective material layer further covers a part of the third interface part, wherein a first display part of the display that corresponds to the first interface part allows the observer to recognize a second optical effect offered by the second optical effect layer when observed at an angle capable of observing regularly reflected light, wherein when illumination light is incident at an angle within a negative angular range and the display is observed at an angle within the negative angular range, the first display part allows the observer to recognize the diffracted light from the first interface part, and wherein the display further comprises a dark light-absorbing layer facing the second optical effect layer with the first optical effect layer interposed therebetween at a portion of the third interface part that is not covered with the reflective material layer.
 2. The display according to claim 1, wherein the reflective material layer covers only a part of the first interface part, and the second optical effect layer further includes, at a position of a second portion of the first interface part that is not covered with the reflective material layer, a portion that faces the first optical effect layer.
 3. The display according to claim 2, wherein the first optical effect layer has light-transmitting properties, and the light-absorbing layer is also present at a position of the second portion of the first interface part.
 4. The display according to claim 3, wherein the light-absorbing layer contains a magnetic substance.
 5. The display according to claim 1, wherein the first interface part, the second interface part, and the third interface part are adjacent to each other, the reflective material layer overlies a first boundary between the first interface part and the second interface part and a second boundary between the first interface part and the third interface part, and the second optical material layer is provided such that an orthogonal projection of the second optical material layer on a main surface of the first optical effect layer that includes the first interface portion, the second interface portion, and the third interface portion overlies the first and second boundaries.
 6. A labeled article comprising: a substrate; and the display according to claim 1 supported by the substrate.
 7. The labeled article according to claim 6, wherein the substrate is a paper and the display is buried in the paper.
 8. The labeled article according to claim 7, wherein the display is in a form of a thread. 